GAS STREAM ODORANT FILTERING APPARATUS AND METHOD

Abstract: Naturel gas odorants contained within a natural gas stream and which have been concentrated at sufficient levels to be a significant health hazard and/or adverse environmental threat are removed from the stream by filtering through a filter assembly (20), which includes a filter media unit (26) containing impingement, absorbing and adsorbing media. The filtered natural gas stream is than passed to an end user's gas appliance. Filter media unit (26) can be periodically removed for disposal of the captured odorant and replaced with a new filter media unit (26).

Description: GAS STREAM ODORANT FILTERING APPARATUS AND METHOD RELATED APPLICATIONS This Appl ication is a con i nuat i on- i n-par t of Serial No. 07/926,45 " ? for "Method for Fi l tering Odorant From A Gas Stream" fi led August 7, 1992, now abandoned, which was a con t i nua t i on- i n- part of the fol lowing Appl ications al l fi led February 22, 1991 which contain related subject matter and are hereby incorporated by reference: S.N. 660,353 for "METHOD AND MEANS FOR FILTERING BENZ- A-ANTHRANCENE FROM A GAS STREAM", now U.S. Pat. 5, 139,543; S.N. 660,343 for "METHOD AND MEANS FOR FILTERING BENZENE FROM A GAS STREAM", now U.S. PAT. 5, 141,533; S.N. 660,346 for "METHOD AND MEANS FOR FILTERING BENZO- A-PYRENE FROM A GAS STREAM", now U.S. PAT. 5,139,542; S.N. 660,345 for "METHOD AND MEANS FOR FILTERING POLY- CHLORI ATED BI PHEYLS FROM A GAS STREAM" , now U.S. PAT. 5,145,494; S.N. 660,350 for "METHOD AND MEANS FILTERI G RADON FROM A GAS STREAM", now U.S. PAT. 5, 149,343. SCOPE OF THE INVENTION The present invention relates to a method of fi l tering. More particularly, it relates to a fi l tering method to el iminate conventional natural gas odorants that had been concentrated within a natural gas distribution network at sufficient levels to be a heal th threat. A a furthe cons aint , the sources of suc odorant concentration are ident i f ied. I t is bel ieved they resul t from aperiodic loading of such ne work in which odorants become clumped into packets due to dampening effects of the compressor driven network and mul tiple customer out let usage that adds the aforement ioned aperiodic loading wi thin the network. DEFINITIONS In this Appl icat ion, "natural gas" means a mixture of gases associated wi th hydrocarbon accumul at ion wi thin the earth as wel l as processed fuel gases derived from petroleum as wel l as mineral products such as coal in ei ther gas or l iquid phases. In some gas l ine networks, the resul t ing f inal gases may be a mixture from these two sources but wherein the essent ial component consists of methane. "Suff icient level to be a heal th threat" means a recogni zed standard for human heal th and safety establ ished by authori tat i e bodies above which cancer or reproduct ive toxici ty in humans resul ts, such bodies to include but not be l imi ted to the U.S. Envi ronmental Protect ion Agency (EPA) , the U.S. Department of Food and Drug Administrat ion (FDA) and the U.S. Department of Commerce. The EPA has set heal th and safety standards for sul f ide type compounds which, i f exceeded, would pose a risk to human heal th . "Adsorpt ion" means f i l ter medi that captures molecules of a gas, l iquid or dissolved substance to the f i l ter su face, by adhes i on . "Absorpt ion" means f i l ter media that absorbs molecules of a gas, l iquid or dissolved substance to the fi l ter i tsel f , by taking in throug pores o interst ices. "Impingement" means f i l ter media that captures molecules of a gas. l iquid, sol id or a dissolved substance to the f i l ter by physical captu e such as by change in veloci ty. BACKGROUND OF THE INVENTION The development of conventional odorants used to identi fy natural gas have undergone an eventful history. Odorants have been added to an otherwise odorless gas to detect i ts presence before becoming a hazard. Pintsch gas condensates were added to most ci ty gas networks in the late 1800's to odori ze water gas. An invest igat ion of odorants for natural gas was undertaken in 1931 by the U.S. Bureau of Mines in associat ion wi th the American Gas Association. As a resul t , eighty-nine substances were evaluated and propert ies for f i fty-seven were measured, see U.S. Bureau of Mines Monograph No. 4, such substances being incorporated herein by reference. The American Gas Associat ion has sponsored subsequent research in which more than 300 materials have been screened. Natural gas at the we I I bore, contains enough hydrocarbons higher than ethane or sul fur bearing const i tuents, (e.g. , hydrogen sul fide, mercaptans etc. ) to be detected easi ly by smel l . But such const i tuents are removed in dehu i d i f i ca t i on and other puri f icat ion processes before entry into the natural gas distribut ion network. Odorizat ion of natural gas is usual ly undertaken for one or more of the fol lowing reasons: ( i ) Customer protect ion wherein the user can smel l a gas leak and obtain assistance to repai r the l ine or equi ment ; ( i i ) Gas leak detect ion in the natural gas network; ( i i i ) State regulat ions wherein more than hal f of the states in the Uni ted States requi re that natural gas have an odor and most states have adopted the Nat ional Fi re Protect ion Associat ion Standards in requi ring odorants wi thin l iquid propane. However, odorants are known to be dangerous. They are known to be corrosive at elevated temperatures such as found in pi lot l i t l ines, burner boxes or combust ion chambers and to produce by-products that are toxic and a danger to heal th. As an example of the latter , mercaptans undergo thermal decomposi t ion to form hydrogen sul f ide, polysul f ideε and the l ike. Amines (wi thin the system as moisture scrubbers) also act as catalysts to increase the efficiency of the above-ment ioned reactions. I have also found that once wi thin a human's body, they do not dissipate and instead bui ld in increments to burden the body to a signi f icant degree, such progression being a funct ion of frequency and level of exposure. Whi le the EPA and various State Agencies may be aware of the problem of odorants in gas I ines, they do not think the reported exposure is of sufficient level to be dangerous. Moreover, odorant concentrat ion levels at a customer end user 's home, business and the l ike are not moni tored. In such si tuat ions, I f ind that surprisingly large concentrat ion of natural gas odorants sporadical ly occur. Sources of such concentrat ion : dampening effects of the compresso -dri en network and mul t iple customer out let usage that add to aperiodic loading of the natural gas stream coupled wi th surprising longevi ty of the in si tu odorants. As a resul t , natural gas odorants can f low to appl iances in the customer's home, business or the l ike at suff icient levels to be a heal th and/or envi ronment l hazard, i .e. exceed Federal and/or State heal th and safety standards. Moreover, al though the original source of gas odorants is the gas phase, both l iquid and gaseous forms can be transported alone or attach to part iculates and form the f inal end-use contamination levels at the appl iance to be used. Convent ional odorants to which the present invent ion relates include mercaptans, al iphat ic su I f ides and cycl ic carbon sul fur ring compounds used alone and in combinat ion wi th each other having potencies resul ting from normal concentrat ions of 0.5 to 1.5 l s. per mi l l ion cubic feet of gas wi thin the gas gathering and distribut ion networks: TYPE CHARACTER! STICS MERCAPTANS TYPICALLY A SH GROUP SUCH AS C2H6SH EXAMPLES, ethyl , propyl , iεopropyl , butyl , teriary butyl and amy I mercaptans ; TYPICALLY A SULfUR MOLECULE ATTACHED ALIPHATIC TO A STRAIGHT CARBON CHAI SULFIDES EXAMPLES: dimethyl , ethyl , diethyl , (THIOETHERS) propyl , isopropyl sul fides SULFUR RING EXAMPLES: thiophane COMPOUNDS SUMMARY OF THE INVENTION The present invention relates to a method of fi l tering, adjacent to the end user's home, business or the I ike such as the adjacent gas distribution and processing system connected to the end user's meter, a gas stream in which a natural gas odorant has been concentrated at suff icient levels to be a significant heal th and/or environmental hazard. Steps of the invention include: (a) introducing the natural gas stream to a fi l ter selected from a group that includes at least activated charcoal and impingement adsorbing and absorbing media whereby natural gas odorants concentrated in the gas stream at sufficient levels to be a health and/or environmental threat by aperiodic loading of such network in which odorants become clumped into packets due to dampening effects of the compressor-d iven equipment and mul tiple customer outlet usage that add to aperiodic loading of the natural gas stream coupled with surprising longevi ty of the in situ odorant, is fi ltered from the gas stream and captured , (b) passing the fi l tered natural gas stream to the customer's gas appl iance wherein safe use of the energy associated with the stream occurs, (c) periodical ly and safely removing the fi l ter of step (a) for disposing of the captured natural gas odorant, (d) inserting a new fi l ter in place of the removed fi l ter of s tep {c ) . DESCRIPTION OF THE DRAWINGS FIG. 1 is side elevation of a gas valve-meter assembly attached at one end to a pipe of a gas l ine network adjacent to a home, business or the l ike, along wi th a f i l tering assembly and by-pass network of the present invent ion; FIG. 2 is a top view of the f i l tering assembly of the invent ion: FIG. 3 is a sect ion taken along l ines 3-3 of FIG. 2; FIG. 4 is an enlarged detai l view taken along l ines 4-4 of FIG. 3; FIG. 5 is an enlarged detai l of the f i l ter media uni t of FIG.3; FIG. 6 is an enlarged detai l of an insert ring used in the fi l ter media uni t of FIG. 3; and FIG. 7 is an al ternate design for the fi l ter unit of FIG. 5. DESCRIPTION OF A PREFERRED EMBODIMENT FIG. 1 i l lustrates a gas meter 10 connected via elbow 11 and gas pipe 12 to a main gas l ine network (not shown) . Downstream of the meter 10 is a tee coupler 14 having a fi rst end 15 connected to an overhead by-pass network general ly indicated at 16, and a second end 17 connected through a first valve 18 and inlet f i tt ing 19 to f i l ter assembly 20. The f i l ter assembly 20 in turn connects via out let f i tt ing 40, elbow 41 and a second valve 42 to the overhead by-pass network 16. As shown, the by-pass network 16 includes a paral lel by-pass val e 43. In operation, the by-pass valve 43 operates in complementary fashion wi th respect to f i rst and second valves 18 and 42, respect i ely. When val e 43 is closed, as shown, the valves 18 and 42 are open and the f i l ter assembly 20 is in operat ion. When valve 43 is open, the valves 18 and 42 are closed and the f i l ter assembly 20 is in a deact ivated state. FIGS. 2, 3 and 4 show the f i l ter assembly 20 in more de t a i I . As shown, the f i l ter assembly 20 includes a cap 21 f i tted wi th a rectangularly cross-sect ioned dome 22 at i ts upper surface 21a, see FIGS. 2 and 4, to which the pipe f i tt ings 19 and 40 attach. The cap 21 also has a lower surface 21b fitted wi th nipples 23 adjacent to a series of passageways that al low entry and egress of the gas stream: ( i ) inlet passageway 24 is L-shaped, is threadably connected to the inlet f i tt ing 19 at one end, and is also connected via central annulus 25 to interior f i l ter media uni t 26 concentric of vert ical axis of symmetry 27; ( i i ) an out let passageway 28 that is bulbous over region 29 but in fluid contact wi th annular gathering region 30 that runs the ful l exterior of the f i l ter media uni t 26; the passageway 28 is then swedged over region 31 ( in a L-shaped output form) at one end of bulbous region 29 for connect ion to out let f i tt ing 40. The cap 21 also has an annular side wal l 21a, see FIG. 4, and inwardly swedged at shoulder 32 and terminates at end 33. I t is threaded therebetween to engage wi th cyl indrical canister 34. The canister 34 includes a side wal l 34a offset from the f i l ter media uni t 26 to form the annular gather ing region 30 previously de cribed and in addi t ion, has shoulders 35 and 36. The region between the shoulders 35, 36 is threaded to engage cap 21. Between shouiders 32 and 35 of the cap 21 and canister 34, respect ively, is grooved O-ring 37 to prevent gas leakage exterior of the f i l ter assembly 20. The lengths of the engaging threaded port ions of the cap 21 and canister 34 are constructed so that posi t ive contact exists only at the O-ring 37 and not at shou I de rs 33 , 36. Canister 34 also includes a bottom wal l 34b. The bottom wal l 34b includes upwardly project ing nipples 38 concentric of a central annulus 39. The latter attach to the fi l ter housing 26. The purpose of the nipples 23 and central annulus 25 of the cap 21 as wel l as that of the nipples 38 and central annulus 39 of the canister 34 is to fixedly receive and hold the fi l ter media uni t 26 relat ive to the cap 21 and canister 34. Note that the di rect ion of the gas stream at the inter ior of the fi l ter assembly 20 is as taught by arrows 45, see FIG. 4. Such gas stream cannot pass di rect ly from inlet passageway 24 to out let passageway 28 but is prevented to such f low due to the length of the annul i 25, 39. Thus the gas flow is in a radial ly expanding, sinusoidal pattern normal to the axis of symmetry 27 about horizontal axis A-A of the f i l ter media uni t 26. The pattern begins at the axis of symmetry 27 and progresses through f i l ter media uni t 26, and ends exterior of the latter at annular gathering region 30. Thus the natural gas odorant is f i l tered from the st rea . FIG. 5 i l lustrates f i l ter media uni t 26 in more detai l . As shown, the f i l ter media uni t 26 includes end pieces 50a, 50b each having a ci rcular notch 51 at outer surface 52 into w ich ni ples 23, 38 of the cap 21 and canister 34, respect ively, are received. Such construct ion permi ts the end pieces 50a, 50b to take up f i rm surface contact wi th the cap 21 and the canister 34 as the cap 21 is threaded to the latter . Interior of the end pieces 50a, 50b are a series of concentric tubes 53, 54, 55, 56 and 57 fi tted into the notches 51 of the former. The tubes 53-57 have side wal ls fi tted wi th perforat ions 59. The side wal ls are normal to the horizontal axis of symmetry A-A previously ment ioned, the latter being also normal to the vert ical axis of symmetry 27. The perforat ions 59 permi t gas f low in the sinusoidal -l ike, single pass f i l tering manner relat ive to axis A-A wi thin the tubes 53-57 as indicated by arrows 45. As shown these arrows 45 begin near the vert ical axis of symmetry 27 and serpent ine outwardly in sinusoidal fashion through the f i l ter media uni t 26. Note that between the tubes 53 and 54; between tubes 54 and 55; between tubes 55 and 56 and between tubes 56 and 57 are separate f i l ter medium 60, 61 , 62 and 63 together forming a four-stage, single pass f i l tering media which in combinat ion remove al l traces of the odorant from the gas stream. The media 60-63 are each selected to remove odorant from the gas stream in progressive fashion, viz. , from microscopic to mi l l imicrospic levels via single passage of the gas stream through each medium 60-63. However, the media 60-63 do not fi l ter the methane from the gas stream. FI LTER MEDIUM 60 In this regard, f i l ter medium 60 is preferably pleated fi l ter paper ha ing the fol lowing characterist ics. Pleated f i l ter paper 60 is widely avai lable, performs impingement , absorpt ion and adsorpt ion and is made by conventional manufacturing processes including but not l imi ted to methods involving weaving of cel lulose, wool , acryl ic, rayon fibers into corrugated sheet form. The tips and troughs of the corrugated pleated fi l ter paper 68 of FIG. 5 are located in accordion fashion across and i thin the tubes 53, 54 but not in contact wi th the upper and lower end pieces 50a, 50b of the f i l ter media uni t . As shown in FIGS. 5 and 6, a separate ring 64 is f i tted in contact wi th each end piece 50a, 50b. The ring 64 of rectangular cross sect ion, includes side wal l 66 and terminat ing broad surface 67, that is compress i ve I y fi tted in snug contact wi th the upper or lower end piece 50a, 50b. As a resul t , the gas stream can ci rculate in the manner shown and pass through the pleated f i l ter paper 60 in single pass fashion between inlet and out let perforat ions 59 associated therewith. The densi ty of paper 60 varies to provide fi l tering of the odorant carried on dust , rust, di rt, moisture and oi l laden part icles in a range of 40 to 750 microns. I t also retains both oi ls and moisture. FILTER MEDIUM 61 In this regard, f i l ter medium 61 is preferably si l ica gel in crystal l ine form located between tubes 54 and 55. Si l ica gel 61 is a convent iona l drying and dehumidi fying agent formed of amorphous si l ica in crystal l ine form for f i l tering and trapping the odorant transported in solut ion wi th water, in gaseous form as wel l as aboard smal ler d iametered di rt and dust part icles carrying odorant piggyback. The gel absorbs moisture wi thin the gas stream but not oi ls and is located between tubes 54 and 55. The medium 61 provides for single passage f i l ter ing operat ions only. Calculat ions associated wi th the above are as fol lows: AVERAGE NATURAL GAS USAGE Assume average gas use is 125 MSCF/YR, then per month usage cuoic meters is 125 mcf/yr/12 = 10,416.6 cu. ft/ month / 35.3 = 295 cu. meters/month Assume the area between tubes 54, 55 is a funct ion of a mean diameter of 3 5/8 inches, a height of 5 inches and thickness of .875 inches, then Fi l ter volume: 52.5 cu. inches; FILTER MEDIUM 62 Fi l ter med ium 62 is preferably open pore polyurethane foam for capturing gas odorants in gaseous form. Fi l ter medium 62 fi l ters by impingement and adsorpt ion and retains micro vapors and sol id part iculates including oi ls and is located between tubes 55 and 56 fo single pass f i l te ing operat ions. I t has the fol lowing characterist ics. Shape: Cyl indrical shape from sheet form Cel lular Matrix Structure Medium densi ty 0.1 to .4 g/cu. cm matrix sol id foam to gas insert Porosi ty-- .14 to .41 ( i .e. 70% to 90 open pore po I yu ret hane ) Sample Period 2 months AT 100 % Retent ion Wel l below breakthrough volume, viz. , the point at which concentrat ion of solute in the column eff luent is hal f the concentrat ion introduced into the column. Vo I a t i I i ty--Med i urn , See below Prepa ra t i on--Cu t from foam sheets; ai r dry; instal l . Pressure Drop--.015 ps i Calculations associated wi th the above are as fol lows: Assume average gas use is 125 MSCF/YR, then per month usage cubic meters is 125 mcf/yr/12 = 10,416.6 cu. ft/ month / 35.3 = 295 cu. meters/month where: .0364 micro g/cu. meter per meter is gas odorant ; Hence: 295 cu . me ter /mon th produces 10.738 micro g/mo of gas odorant ; And : .0027612 cu. cm requi red to remove above am ' t of gas odorant Fi l ter volume^ 403.28 cu. cm via 5 inches height by 1/2 inches thickness by 15.7 inches long; Ef f i c i ency--700 cu. meters avai lable Change frequency wel l wi thin above pattern FI LTER MEDIUM 63 Furthermore, f i l ter medium 63 is preferably granular act ivated charcoal located between tubes 56 and 57 for single pass fi l tering operat ions. Granular activated charcoal is a conventional fi l tering medium, performs f i l tering on l iquids, gases and sol id part icul ates down to 10 Angstroms in size (but does not retain water) by impingement and adsorpt ion and is prepared by carbonizat ion of raw mater ials such as wood, coconut shel l and coal . I t attracts and holds the gas odorant i rrespect ive of the mode of transport such as a l iquid or gas alone or piggyback aboard di rt and dust part icles as wel l as wi th l iquid plugs. Physical propert ies: Surface Area = 600 to 1050 cubic meters per gm Densi ty = .92 to 2.0 grams per cubic meter Effect ive size = .8 to 1.5 mm Pore volume = .6 to 1.7 cubic cm per gram Mean diameter = 1.2 to 1.7 mm Sieve Size = No. 8 to No. 40 (U.S. Series) Iodine No . = 650 to 1 , 000 Calculat ions associated wi th the above are as fol lows: Assume average gas use is 125 MSCF/YR, then per month usage cubic meters is 125 mcf/yr/12 = 10,416.6 cu. ft/ month / 35.3 = 295 cu. meters/month Assume the area between tubes 54, 55 is a funct ion of a d iameter of 7 inches, a height of 5 inches and a thickness of .5 inches, then Fi l ter vo I ume= 55. cu. inches; Densi ty of GAC = .30 oz./cu. in GAC Av i a i i = 16.5 oz . Requi rement to remove gas odorant associated wi th 295 cu. meters is wel l wi thin above change pattern. FIG. 7 i l lustrates al ternate fi l ter media uni t 69 in detai l . As shown, the f i l ter media uni t 69 is simi lar to the f i l ter media uni t 26 previously described, such f i l ter media uni t 69 having end pieces 70, 71 f i tted wi th inwardly facing notches 72 (relative to a horizontal axis of symmetry, not shown) , and a series of concentric tubes 73, 74, 75, 76 and 77 col l inear with axis of symmetry 78. However, perforat ions 79 are provided in side wal ls of tubes 73-77 to al low radial f low outwardly from vert ical axis of symmetry 72. Such construct ion does not permi t the sinusoidal f low as previously mentioned, however. Instead, a gas stream f lows as an annular mass through the f i l ter media uni t 69 beginning at the axis of symmetry 78 and ending at the exterior of tube 77. Such pattern is indicated by arrows S that are seen to expand outwardly from the axis of symmetry 78. The notches 72 aid in assembly as they take up f i rm surface contact wi th the cap 21 and canister 27 of FIGS. 2, 3 and 4, as the former and latter are threaded together. Between the tubes 73 and 74; between tubes 74 and 75; between tubes 75 and 76, and between tubes 76 and 77 are separate fi lter medium 80, 81, 82 and 83 together forming a four-stage fi l tering media which in combination remove the gas odorant from the gas stream. That is, the media 80, 81, 82 and 83 are selected to remove al l traces of the gas odorant from the gas stream in the same order and simi lar fi ltering capacity as previously discussed with reference to FIG 5. In this regard, fi l ter medium SO is pleated paper, medium 81 is si l ica gel , medium 82 is open pore polyurethane foam and medium 83 is granular activated charcoal each having characteristics as set fort above . GUIDELINES FOR SELECTION OF FILTER MEDIA 60-63 & 80-83 Natural gas odorant exists in two states within the gas l ine network: primari ly as a l iquid and as a vapor. I t is carried along because of the pulsation of the gas stream and surprisingly because of the gas phase transition effects created by the drive compressors of the gas system augmented by the multiple outlet demands of the customers. But no matter how the gas odorant is carried in the gas stream, the former are trapped within the fi lter media 60-63 and 80-83 of the invention. Gas phase transition is a l ittle understood phenomenon in which various dynamics due to changes in temperature, pressure, pipe size, flow rates that cause interaction between hazardous elements of the gas stream and various other elements in the network, such as ipe coat ings, plug flows (aggregations of materials moving as a group) l iquids and gaseous phases of consti tuents of the natural gas stream. As a resul t , l iquids and gases wi thin the natural gas stream surprisingly change state. The resul t ing gaseous phase may contain the hazardous elements which are transported great distances. As a vapor or l iquid, the gas odorant is then carried along under l ike sets of ci rcumstances described above. PRESSURE CONDITIONS As surface residue on sol id particula es, the gas odorant is carried along as fol lows. At the wel l si te, pressures in access of 2,000 psi occur. Such pressure can be maintained unti l stepped down to approximately 1 ,000 psi , thence to 60 psi and f inal ly to 1/2 to 2 psi at the user 's residence and about 5 psi for some business uses. Whi le fi l ter media 60-63 and 80-83 are preferably as discussed above, substi tutions can be made. For example, other types of imp i ngemen t-adsorb i ng media could be used including si l ica sand, act ivated clay such as on tmo r i I I an i te , natural zeol i tes composed of hydrous calcium and aluminum si l iceous materials, synthet ic zeol i tes cal led molecular sieves such as sodium aluminum si l icates, catl in si l t loam, dried corn husks, etc. Also, fluid baths, sonic col lectors, elect ostatic prec i i ta to rs and thermal de-humi d i f i ca t i on devices could also be used . Other impingement adsorbing media includes other packings such as can be woven, coated or impregnated (such as wi th glycerol , glycerin, oi ls, glycol etc. ) . Other types of f i l ters include membrane f i l ter media for use in natural gas envi ronments general ly above 100 psi in which the solute is the force that helps perform the f i l tering, as wel l as special f i l ters such as elongated, i n ter- I a 11 i ced baff les that provide electrostat ic col lect ion such as the HEPA f i l ter (High Eff iciency Part icle Accumulator f i l ter, an acronym of The Nat ional Aeronaut ics and Space Ad inistrat ion) . In some appl icat ions, f luid baths could be used, in which fluids selected from a group that includes water, oi l , alcohol , glycerol , glycerin, and glycol , could be used. Such use would requi re a modi ficat ion to the canister 27 in order to provide a f i l tering operat ion. FURTHER METHOD ASPECTS After instal lation has occurred, the fi l ter system is an act ive f i l tering state for natural gas odorants. That is to say, the valve 43 in the by-pass network 16 is closed and the valves 18 and 42 upstream and downstream of the f i l tering assembly 20 a re opened . When the fi l tering assembly 20 is to be re-charged, the valve 43 in the by-pass network 16 is opened so that gas is passing in paral lel to the downstream appl iances (not shown) . T is assures ample gas supply before the f i l tering assembly 20 is deact ivated. Such deact ivat ion occurs when the valves 18 and 42 are closed. Then the canister 27 wi th the f i l ter media 60-63 & 80-83 captured wi thin i ts side wal l 31 , is removed from contact wi th cap 21 , and the canister 27 and f i l ter media 60-63 & 80-83 are removed for transport to a waste stat ion and disposal . A new canister 27 wi th new f i l ter media 60-63 or 80-83 is re-attached. The above descript ion contains several speci f ic embodiments of the invent ion. I t is not intended that such be construed as l imi tat ions on the scope of the invent ion, but merely as examples of preferred embodiments. Persons ski l led in the art can envision other obvious possible variat ions wi thin the scope of the descript ion. For example, the f i l ter assembly 20 can be inserted in higher pressure l ines of the gas transfer network, such as wi thin the local ut i l i t ies' piping network. Hence the scope of the invention is to be determined by the appended claims and thei r legal equivalents. MOD I FI CAT ION Radon radioactive decay products can pose an especial ly potent heal th risk as disclosed in my U.S. Pat. 5, 149,343 for "Method for Fi l tering Radon From a Gas Stream" issued September 22, 1992. In this regard, a recent study indicates several of the isotope daughters of radon readi ly adhere to surfaces, including wal ls, furni ture and ai rborne part icles and pose a heal th risk to both act ive and passive smokers. (See "SCIENCE NEWS", August 3, 1991 , Pg. 79 "ELEVATED RADON RISK FOR PASSIVE SMOKER") . In this regard, I have discovered a surprising high radon risk for humans in associat ion wi th odorant in natural gas. I t is bel ieved such odorant prolongs the stay of such radon daughters an undue and surprising t ime period. Hence, such daughters remain avai lable for inhalat ion wi thin the human body as aperiodic loading wi thin the natural gas gathering and distributing network of the radon daughte s and odorant occurs. Radon daughters are known to have an ionic charge. However, only recent ly thei r elevated risk in association wi th cigarette smoke has been documented. In simi lar fashion I have discovered that odorant in natural gas and such radon decay products pose independent heal th risks and together form a potent synergist ic duo that pose an unacceptable heal th risk. Thei r combinat ion can occur in the distribut ion system of the natural gas distributor before the radon daughter-odo ran t combination enters the user's interior distribution subsystem. Hence, when such combinat ion is igni ted at the user's appl iance, a signi f icant heal th risk occurs.

Claims: CLAIMS 1. A method of f i l tering, adjacent to an end user-customer 's residence or business, a natural gas stream in which a natural gas odorant has been concentrated at suff icient levels to be an adverse envi ronmental threat in a natural gas gathering and distributing network, comprising the steps of: (a) introducing the natural gas stream to a fi l ter selected from a group that includes impingement, absorbing and adsorbing media whereby natural gas odorant concentrated in the gas stream at sufficient levels to be an adverse environmental threat by aperiodic loading of the natural gas wi thin the gathering and distribut ing network, is fi l tered from the gas stream and captured i rrespective of mode of transport, (b) passing the fi l tered natural gas stream to the customer's gas appl iance wherein safe use of the energy associated wi th the stream occurs, (c) periodical ly and safely removing the f i l ter of step (a) for disposing of captured natural gas odorant, (d) insert ing a new f i l ter in place of the removed fi l ter of step (c ) . 2. The method of Claim 1 in which said impingement , absorbing and adsorbing media of step (a) for fi l tering said natural gas odorant , are selected from the group comprising pleated fi l ter paper, si l ica gel , open pore polyurethane foam and granular act ivated charcoal . 3. The method of Claim 2 in which said impingement , absorbing and adsorbing media of step (a) comprises in serium, pleated f i l ter paper , si l ica gel , open pore polyurethane foam and granular activated charcoal whereby said natural gas odorant is surprisingly removed from the natural gas stream. 4. The method of Claim 1 in which step (a) is further characterized by aperiodic loading of in si tu natural gas odorant being the esul t of gas phase transi t ion effects occurring wi thin the natural gas gathering and dist ibution network. 5. The method of Claim 4 in which the aperiodic loading of step (a) is the resul t of dampening effects of compressor-d iven equipment and usage of mul tiple out lets connected to the compressor-driven equipment wi thin the natural gas gathering and distribut ing network. 6. The method of Claim 5 in which the fi l tering occurs after the natural gas stream exi ts from the end user-customer's gas meter connected to one of the mul tiple outlets of the natural gas gathering and distributing network. 7. The method of Claim 1 in which the fi l tering occurs wi thin the natural gas gathering and distribut ing network. 8. A method of fi l tering adjacent to an end-customer's residence or business in which at least a single gas appl iance is located, a natural gas stream in which a natural gas odorant has been concentrated at a suff icient level to be an adverse environmental threat wi thin a natural gas gathering and distributing network connected to the end user-customer's gas appl iance comprising the steps of : (a) introducing the natural gas stream to a f i l ter selected from a group that includes impingement , absorbing and adsorbing media whereby natural gas odorant concentrated in the gas stream at a sufficient level to be an adverse envi ronmental threat due to aperiodic loading of the natural gas wi thin the gathering and distribut ing network, is f i l tered from the gas stream and captured irrespect ive of mode of transport, (b) passing the fi l tered natural gas stream to the customer's gas appl iance wherein safe use of the energy associated wi th the s t ream occurs . 9. The method of Claim 8 wi th the addi tional steps of : (c) periodical ly and safely removing the fi l ter of step (a) for disposing of captured natural gas odorant, (d) insert ing a new f i l ter in place of the removed f i l ter of step ( c ) . 10. The method of Claim 8 in which said impingement, absorbing and adsorbing media of step (a) for f i l tering said natural gas odorant, are selected from the group comprising pleated fi l te paper, si l ica gel , open pore polyurethane foam and granular act ivated charcoal . 11. The method of Claim 10 in which said impingement, absorbing and adsorbing media of step (a) comprise in serium, pleated fi l ter paper, si l ica gei , open pore polyurethane foam and granular activated charcoal whereby said natural gas odorant is surprisingly removed from the natural gas stream. 12. The method of Claim 8 in which step (a) is further characterized by aperiodic loading of in si tu natural gas odorant being the resul t of gas phase transi t ion effects occurring wi thin the natural gas gathering and distribut ion network. 13. The method of Claim 12 in which the aperiodic loading of step (a) is the resul t of dampening effects of compressor-dri en equipment and usage of mul t iple out lets connected to the compressor-driven equipment wi thin the natural gas gathering and distribut ing network. 14. The method of Claim 9 wherein steps (a) , (c) and (d) occur after the natural gas stream exi ts from one of a series of mul tiple out lets of the natural gas gathering and distributing network and from a gas meter connected to said one of the mul t iple out lets. 15. The method of Claim 9 in which step (a) , (c) and (d) occur wi thin the natural gas gathering and distribution network. 16. A method of fi l tering adjacent to an end user-customer's residence or business in which at least a single gas appl iance is located, a natural gas stream in which a natural gas odorant and radon have been concentrated at suff icient levels to an adverse envi ronmental threat wi th a natural gas gathering and distributing network connected to the end user-customer's gas appl iance, comprising the steps of: (a) introducing the natural gas stream to a fi l ter selected from a group that includes impingement, absorbing and adsorbing media whereby natural gas odorant and radon concentrated in the gas stream at suff icient levels to be an adverse envi ronmental threat due to aperiodic loading of the natural gas wi thin the gathering and distri ut ing network, is f i l tered from the gas stream and captured i rrespective of mode of transport , (b) passing the fi l tered natural gas stream to the customer's gas appl iance wherein safe use of the energy associated wi th the s t ream occurs . 17. The method of Claim 16 wi th the addi tional steps of : (c) periodical ly and safely removing the fi l ter of step (a) for disposing of captured natural gas odorant and radon, (d) insert ing a new fi l ter in place of the removed f i l ter of step ( c ) . 18. The method of Claim 16 in which said impingement , absorbing and adsorbing media of step (a) for f i l tering said natural gas odorant and radon, are selected from the group comprising pleated f i l ter paper, si l ica gel , open pore polyurethane foam and granular act ivated charcoal . 19. The method of Claim 17 in which the natural gas gathering and distributing network includes gas meters each connected to one of a series of mul tiple outlets of the natural gas gathering and distributing network and wherein steps (a) , (c) and (d) occur after the natural gas stream exi ts from the end user-customer's gas meter . 20. The method of Claim 17 in which steps (a) , (c) and (d) occur wi thin the natural gas gathering and distribut ing network.

Inventors: SOWINSKI RICHARD F, SOWINSKI, RICHARD, F.
Applicants: SOWINSKI RICHARD F, SOWINSKI, RICHARD, F.
Application year: 1994
Main classification: B01D53
IPC codes: B01D53